Headaches are a common ailment, and usually nothing to worry about.
But in some cases, they are the first sign of a deadly condition such as a bleed on the brain or even a cancerous tumour.
Now, one US-based doctor has taken to Instagram to advise how to tell the difference between a sinister head pain, and a harmless one.
Neurologist Dr Baibing Chen said two specific symptoms are a telltale red flag.
‘If a headache suddenly feels different, such as thunderclap headache, or it’s lasting longer [than usual] it could be of something serious like a bleed or tumour or aneurysm,’ he said.
Named after a the weather phenomenon, thunderclap headaches are sudden agonising pains that feel similar to being hit in the head, resulting in ‘blinding pain unlike anything experienced before’ according to the NHS.
This is considered a medical emergency, and the health service advises sufferers to call 999 or get to A&E.
A sudden thunderclap headache may be a sign of a burst blood vessel in the brain, which can result in lifelong disability, coma and even death.
Headaches can also be a sign of a brain tumour, so medics typically advise visiting the GP if headaches become new or more frequent.
As well as revealing red flags of brain disorders, Dr Chen offered his social media followers ways of preventing neurological conditions – including terrifying ‘locked in syndrome’.
This happens when the brainstem is severely damaged, causing the paralysis of voluntary muscles, except for those that control your vertical eye (up and down) movements.
Those with the disorder are conscious and have usual cognitive abilities, but they cannot speak or move.
Dr Chen said neck manipulation – a technique carried out by some chiropractors – could put patients at risk of developing the life-wrecking disease.
The treatment involves manually manipulating the bones in the upper spine to relieve neck pain.
Dr Chen said he would never undergo such a technique himself due to the serious, albeit small, risk of something going terribly wrong.
‘Forceful neck adjustments can carry a rare but serious risk, and that is vertebral artery dissection,’ he said.
This is a tear in one of the arteries in the neck that feeds the brainstem oxygen rich blood. Such an injury carries the risk of causing a stroke.
Dr Chen continued: ‘A stroke in the brainstem can lead to one of the scariest things I’ve ever seen and it’s called “locked-in syndrome”, where you’re fully aware but can’t move or speak.’
Last on the medic’s ‘never list’ was missing out on regular good quality sleep.
‘Chronic sleep deprivation can increase the risk of dementia and lead to a host of neurological issues,’ he said.
‘So even with a busy schedule at the hospital and coming home to two little kids I try my best to get quality sleep and get at least six hours when I can.’
The NHS advises that most adults need about seven to nine hours of good quality sleep per day.